Outlook EnableUnsafeClientMailRules Setting Enabled - Registry

Status: test
Severity: high
Log source: category registry_set, product windows
Author: Nasreddine Bencherchali (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros

MITRE ATT&CK coverage

Tactic	Techniques
Persistence	`T1112` Modify Registry
Defense Impairment	`T1112` Modify Registry

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 13: RegistryEvent (Value Set)

Rule body

title: Outlook EnableUnsafeClientMailRules Setting Enabled - Registry
id: 6763c6c8-bd01-4687-bc8d-4fa52cf8ba08
related:
    - id: c3cefdf4-6703-4e1c-bad8-bf422fc5015a
      type: similar
    - id: 55f0a3a1-846e-40eb-8273-677371b8d912 # ProcCreation variation
      type: similar
status: test
description: Detects an attacker trying to enable the outlook security setting "EnableUnsafeClientMailRules" which allows outlook to run applications or execute macros
references:
    - https://support.microsoft.com/en-us/topic/how-to-control-the-rule-actions-to-start-an-application-or-run-a-macro-in-outlook-2016-and-outlook-2013-e4964b72-173c-959d-5d7b-ead562979048
    - https://speakerdeck.com/heirhabarov/hunting-for-persistence-via-microsoft-exchange-server-or-outlook?slide=44
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-02-08
modified: 2023-08-17
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1112
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: '\Outlook\Security\EnableUnsafeClientMailRules'
        Details: 'DWORD (0x00000001)'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    TargetObject|endswith: '\Outlook\Security\EnableUnsafeClientMailRules'
    Details: 'DWORD (0x00000001)'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Details`	eq	`DWORD (0x00000001)` corpus 40 (sigma 36, chronicle 4)	`field:"Details" kind:eq value:"DWORD (0x00000001)"`
`TargetObject`	ends_with	`\Outlook\Security\EnableUnsafeClientMailRules`	`field:"TargetObject" kind:ends_with value:"\Outlook\Security\EnableUnsafeClientMailRules"`